Conventionally, as a transmission of this type, a transmission has been known that includes: first, second, and third planetary gears arranged in sequential in order in the axial direction; and a brake that can connect a first carrier of the first planetary gear and a second ring gear of the second planetary gear disposed between the first and the third planetary gears to a transmission case to hold the first carrier and the second ring gear stationary (see Patent Document 1, for example). In this transmission, friction engagement plates constituting the brake are disposed so as to surround at least part of the first planetary gear. The first carrier and the second ring gear are coupled together via a coupling member extending from the second ring gear toward the inner peripheral side, and the second ring gear is coupled to a brake hub constituting the second brake via the first carrier. Furthermore, at least either one of a fitting portion between the outer peripheral portion of the coupling member and the second ring gear and a fitting portion between the inner peripheral portion of the coupling member and the first carrier is structured as a fitting portion without an aligning function. The coupling member is fitted onto at least either one of the second ring gear and the first carrier with radial play therebetween.
In the transmission thus structured, by the coupling member extending toward the inner peripheral side from the second ring gear, the first carrier of the first planetary gear and the second ring gear of the second planetary gear are coupled together at a position closer to the central axis of the transmission. This makes it possible to prevent vibrations excited in the second ring gear by engagement with the pinion gear from being transmitted to the case via the brake when the second ring gear is held stationary to the case by the brake. By coupling the first carrier to the brake hub of the brake, the path from the second ring gear to the brake can be lengthened. This makes it possible to satisfactorily damp vibrations excited in the second ring gear when the second ring gear of the second planetary gear is held stationary to the case by the brake. Furthermore, by fitting the coupling member onto at least either one of the second ring gear and the first carrier with radial play therebetween, the aligning function of the second planetary gear can be prevented from being adversely affected by engagement of the brake. Consequently, an excessive force caused by axial center displacement among rotating elements of the second planetary gear can be prevented from being generated during engagement of the brake, and vibrations excited in the ring gear during engagement of the brake can be satisfactorily reduced.